1. Field of the Invention
This invention relates to the field of Radio Frequency Identification (RFID) tags and labels, and in particular to antenna structures for such tags and labels, and methods of reducing costs of antenna structures.
2. Description of the Related Art
Radio frequency identification (RFID) tags and labels (collectively referred to herein as “devices”) are widely used to associate an object with an identification code. RFID devices generally have a combination of antennas and analog and/or digital electronics, which may include for example communications electronics, data memory, and control logic. For example, RFID tags are used in conjunction with security-locks in cars, for access control to buildings, and for tracking inventory and parcels. Some examples of RFID tags and labels appear in U.S. Pat. Nos. 6,107,920, 6,206,292, and 6,262,292, all of which are hereby incorporated by reference in their entireties.
As noted above, RFID devices are generally categorized as labels or tags. RFID labels are RFID devices that have a surface attached directly to an object, adhesively or otherwise. RFID tags, in contrast, are secured to objects by other means, for example by use of a plastic fastener, string or other fastening means.
The RFID devices generally utilize an antenna structure that is operatively coupled to electrical or electronic components, in the form of a chip or a strap (such as is described in U.S. Pat. No. 6,606,247), to communicate with a receiver or transceiver device such as a detector or reader. The antenna structure utilizes conductive material arranged on a dielectric substrate in a suitable array. The antenna structure is coupled to the chip or strap to allow communication between the RFID device and the reader and the detector. A wide variety of antenna sizes, shapes, and configurations may be utilized to achieve various communication characteristics, depending on many factors.
The conductive material of the antenna structure may be attached on the dielectric substrate by any of a variety of suitable methods. One such method involves printing of a conductive ink to form the antenna structure. Such conductive inks may include any of a variety of suitable electrically conductive materials, including conductive metal particles, carbon particles, or conductive polymer particles.
The cost of RFID devices has been a significant barrier to more widespread use of such devices. One component of the cost is the cost of materials for the antenna structure, such as the cost for the conductive ink that may be used to print the antenna structure. Accordingly it would be advantageous to achieve cost reductions in RFID devices, such as by reducing the expense of materials utilized, or by otherwise reducing fabrication costs.